Which of the following reactions can be used to make ethyl
isocyanide?

Options

A. `CH_3 CH_2 NH_2 + CHCI_3 underset(Delta) overset("KOH") (to)`
B. `CH_3 CH_2 Br + AgCN to`
C. `CH_3 CH_2 - NH - underset(underset(O)(||))C - H overset("POCI"_3)to`
D. `CH_3 CH_2 Br + KCN to`

Explanation

To determine which reactions can be used to make ethyl isocyanide, we will analyze each reaction step by step.

### Step 1: Analyze the First Reaction
**Reaction:** CH3CH2NH2 + CHCl3 + 3 KOH (alcoholic, heated)

- **Starting Material:** Ethyl amine (CH3CH2NH2)
- **Reagents:** CHCl3 (chloroform) and KOH (potassium hydroxide)
- **Process:** When ethyl amine reacts with chloroform in the presence of alcoholic KOH and is heated, it undergoes a process known as the "isocyanide synthesis" or "carbylamine reaction."
- **Product Formation:** The reaction produces ethyl isocyanide (CH3CH2N=C), along with byproducts such as KCl and water.

**Conclusion:** This reaction can produce ethyl isocyanide.

### Step 2: Analyze the Second Reaction
**Reaction:** CH3CH2Br + AgCN (in C2H5OH, heated)

- **Starting Material:** Ethyl bromide (CH3CH2Br)
- **Reagents:** Silver cyanide (AgCN) in ethanol
- **Process:** In this reaction, ethyl bromide reacts with silver cyanide to form ethyl isocyanide.
- **Product Formation:** The reaction produces ethyl isocyanide (CH3CH2N=C) and AgBr as a byproduct.

**Conclusion:** This reaction can also produce ethyl isocyanide.

### Step 3: Analyze the Third Reaction
**Reaction:** CH3CH2NHCOH + POCl3

- **Starting Material:** Ethyl carbamate (CH3CH2NHCOH)
- **Reagents:** Phosphoryl chloride (POCl3)
- **Process:** When ethyl carbamate reacts with POCl3, it undergoes a transformation that leads to the formation of ethyl isocyanide.
- **Product Formation:** The product formed is ethyl isocyanide (CH3CH2N=C).

**Conclusion:** This reaction can also produce ethyl isocyanide.

### Step 4: Analyze the Fourth Reaction
**Reaction:** CH3CH2Br + KCN (alcoholic, heated)

- **Starting Material:** Ethyl bromide (CH3CH2Br)
- **Reagents:** Potassium cyanide (KCN) in alcoholic medium
- **Process:** In this case, ethyl bromide reacts with potassium cyanide to form ethyl cyanide (nitrile), not isocyanide.
- **Product Formation:** The product formed is ethyl cyanide (CH3CH2C≡N) and KBr as a byproduct.

**Conclusion:** This reaction does not produce ethyl isocyanide.

### Final Answer
The reactions that can be used to make ethyl isocyanide are:
1. CH3CH2NH2 + CHCl3 + 3 KOH (alcoholic, heated)
2. CH3CH2Br + AgCN (in C2H5OH, heated)
3. CH3CH2NHCOH + POCl3